feat: add simple Express app with /hello endpoint and tests

src/greeting.js

@@ -0,0 +1,5 @@
+function getGreeting() {
+  return 'Hello world';
+}
+
+module.exports = { getGreeting };

src/server.js

@@ -0,0 +1,17 @@
+const express = require('express');
+const { getGreeting } = require('./greeting');
+
+const app = express();
+const PORT = process.env.PORT || 3000;
+
+app.get('/hello', (req, res) => {
+  res.send(getGreeting());
+});
+
+if (require.main === module) {
+  app.listen(PORT, () => {
+    console.log(`Server listening on port ${PORT}`);
+  });
+}
+
+module.exports = app;

tests/e2e/e2e.test.js

@@ -0,0 +1,24 @@
+const axios = require('axios');
+const app = require('../../src/server');
+let server;
+let baseURL;
+
+beforeAll(done => {
+  server = app.listen(0, () => {
+    const { port } = server.address();
+    baseURL = `http://127.0.0.1:${port}`;
+    done();
+  });
+});
+
+afterAll(done => {
+  server.close(done);
+});
+
+describe('E2E GET /hello', () => {
+  it('responds with Hello world', async () => {
+    const res = await axios.get(`${baseURL}/hello`);
+    expect(res.status).toBe(200);
+    expect(res.data).toBe('Hello world');
+  });
+});

tests/integration/app.test.js

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+const request = require('supertest');
+const app = require('../../src/server');
+
+describe('GET /hello', () => {
+  it('should return Hello world', async () => {
+    const res = await request(app).get('/hello');
+    expect(res.statusCode).toBe(200);
+    expect(res.text).toBe('Hello world');
+  });
+});

tests/unit/greeting.test.js

@@ -0,0 +1,7 @@
+const { getGreeting } = require('../../src/greeting');
+
+describe('getGreeting', () => {
+  it('returns the hello world message', () => {
+    expect(getGreeting()).toBe('Hello world');
+  });
+});